The present invention relates to a pressure sensitive adhesive composition and its application.
The majority of pressure sensitive adhesives disclosed by the prior art are tacky to the touch and present difficulties in storage and handling because they tend to exhibit "blocking" properties, i.e., they tend to adhere to themselves when stored on a reel. Thus, there exists a need for a pressure sensitive adhesive that is initially tack-free, but forms a permanent bond upon moderate sealing pressure.
U.S. Pat. No. 4,889,884 to Dust et al. discloses an adhesive that is capable of forming a seal to itself with application of pressure, yet resists blocking. However, Dust et al. does not disclose the presence of a filler. As a result, silicone oil, often used in the nip for cut sheet forms to protect the fused roll, would be expected to migrate to the surface of the adhesive and interfere with the sealing operation. Thus, there is an additional need for a pressure sensitive adhesive whose adhesive properties will not be adversely affected by contact with silicone oil.